JP2000301598A - Matched die molding method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the lowering of attaching accuracy or appearance caused by the generation of unevenness on the rear surface of a recessed bent part in a matched die molding method for molding a plate-shaped product from a molten resin sheet. SOLUTION: A matched die molding apparatus is equipped with a lower mold 10 having a first molding surface which has a recessed part 11a formed on the upper side thereof and an upper mold 20 provided so as to be able to approach and separate with respect to the lower mold 10 and having a second molding surface 21 which holds an almost constant gap with respect to the first molding surface 11 at the most approach position formed on the rear side thereof. A molten resin sheet 30m thinner than the gap is supplied so as to cover the first molding surface 11 to be brought into close contact with the almost all surface of the first molding surface 11 and both molds are set to the most approach position to bring the molten resin sheet becoming the vicinity of the bottom part of a recessed part into close contact with the second molding surface 21 and, subsequently, the molten resin sheet 30m becoming a part other than the vicinity of the bottom part of the recessed part is brought into close contact with the second molding surface 21. The close contact operations of the molten resin sheet under suction are performed by the first and second passages 15A, 15B and upper passage 25 formed in the lower and upper molds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matched die forming method for forming a plate-like product from a molten resin sheet and a matched die forming apparatus used for the method.

[0002]

2. Description of the Related Art As such a matched die forming apparatus, there is, for example, one shown in FIGS. The lower mold 1 having the first molding surface 2 formed on the upper side, the upper mold 20 having the second molding surface 21 formed on the lower side so as to be able to approach and separate from the lower mold 1, It comprises a supply die 35 for supplying the molten resin sheet 30m from the supply device.

A large concave portion 2a is formed on the molding surface 2 of the lower die 1, and a convex portion 21a corresponding to the concave portion 2a is formed on the second molding surface 21 of the upper die 20, so that the two dies 1 and 20 are closest to each other. At the position (see FIGS. 5 and 6), the gap between the molding surfaces 2 and 21 is almost constant. In the intermediate chamber 6 formed in the lower mold 1, a large number of small suction holes 7 (for example, having a hole diameter of about 0.3 mm and a pitch of about 30 mm) opened in the first molding surface 2 are provided.
And the lower port 8 opening to the lower surface are communicated.
0, the second intermediate surface 21
A number of narrow upper suction holes 27 opening to the upper side and an upper port 28 opening to the upper surface are communicated. The intermediate chamber 6, the suction hole 7, and the lower port 8 form a lower passage 5, and the upper intermediate chamber 26, the upper suction hole 27, and the upper port 28 form an upper passage 25. The design surface of the plate-shaped product 30 to be molded (the surface that becomes the front side in the used state) is formed by the second molding surface 21 of the upper die 20.

The supply die 35 has a slender shape extending in a direction perpendicular to the paper surface in FIG. 3 and projects over the lower mold 1 and moves to supply the molten resin as the base material 31 and the molten resin as the skin 32. Two supply pipes 36 and 37 are provided. The materials of the base material 31 and the skin 32 are both polyolefin-based synthetic resins (for example, polypropylene).

A description will be given of a case where the plate-shaped product 30 is formed by such a conventional matched die forming apparatus. Each synthetic resin material in a molten state supplied to the supply die 35 from each of the supply pipes 36 and 37 has a predetermined width composed of the base material molten resin layer 31m and the skin molten resin layer 32m that are joined together and integrally superposed. Molten resin sheet 3 rich in plasticity
0 m (the thickness of both molding surfaces 2 and 2 in the closest state)
1 (smaller than the gap between the two), and is extruded from an elongated slit-like extrusion port on the lower side of the supply die 35.
By moving the supply die 35 in the horizontal direction to the right in FIG. 3 while extruding the molten resin sheet 30m, the molten resin sheet 30m becomes the base resin molten resin layer 31m.
It is supplied so as to cover the entire first molding surface 2 of the lower mold 1 with the side down. Since the molten resin sheet 30m is in a molten state and is rich in plasticity, as shown by a solid line and a two-dot chain line in FIG. 3, the shape as a whole is along the first molding surface 2; 2a and the concave corners on both sides are in a state of floating from the first molding surface 2.

After this supply, a negative pressure from a vacuum source (not shown) is applied to the lower passage 5 of the lower mold 1 via the lower port 8 so that the molten resin sheet 30m is shown by a solid line in FIG. Thus, the entire surface is brought into close contact with the first molding surface 2 of the lower mold 1 by suction. Next, the supply die 35 is completely retracted to the side from above the lower die 1, and then the upper die 20 is lowered to the closest position as shown in FIG. In this state, the protruding portion 22 on the outer periphery of the upper mold 20 abuts on the upper surface of the outer periphery of the lower mold 1, and unnecessary portions on the outer periphery of the molten resin sheet 30 m are cut off. There is a slight gap between 32 m and the second molding surface 21 of the upper mold 20.

Next, the negative pressure from the vacuum source is applied to the upper port 2
8 to the upper passage 25 of the upper die 20 to apply a negative pressure between the molten resin sheet 30m and the second molding surface 21. At the same time, the application of the negative pressure to the lower passage 5 is stopped and By communicating the side port 8 with the atmosphere, the molten resin sheet 30m is sucked toward the upper mold 20 as shown in FIG.
The skin molten resin layer 32m is in close contact with the second molding surface 21.
Then, the molten resin sheet 3 is cooled by natural cooling or forced cooling.
The temperature is reduced by 0 m to cure the base material 31 and the skin 32.
When the plate-shaped product 30 is formed, the upper passage 25
Is stopped and the upper port 28 is communicated with the atmosphere, and then the upper mold 20 is raised to take out the plate-like product 30.

As described above, the reason why the molten resin sheet 30m is brought into close contact with the second molding surface 21 by suction (FIG. 6) is to shape the surface of the skin molten resin layer 32m serving as a design surface into a predetermined shape. In addition, prior to this, the molten resin sheet 30m is brought into close contact with the first molding surface 2 of the lower mold 1 by suctioning the molten resin sheet 30m raised from the first molding surface 2 as described above.
The lower part of the upper mold 20 descending to the part m (see FIG. 1) locally hits the lower part of the upper mold 20 to form the molten resin sheet 30m (especially, the skin molten resin layer 32m on the design surface side) with an irregular thickness. This is to prevent the quality of the plate-shaped product 30 from deteriorating.

[0009]

The molten resin sheet 30m
A state in which the molten resin sheet 30m is in close contact with the first molding surface 2 due to a negative pressure acting between the first molding surface 2 and the second molding surface 21 (FIG. 5).
When the molten resin sheet 30m shifts from the state in which the molten resin sheet 30m is brought into close contact with the second molding surface 21 (FIG. 6), the flat portion of the molten resin sheet 30m moves more easily in the thickness direction than the strongly bent portion. Therefore, in the molten resin sheet 30m, the flat portion having a small curvature is first moved from the first molding surface 2 side to the second molding surface 21 side to be in close contact therewith, and the bent portions 30a, 30b, 30c, 30 having large curvatures are brought into close contact.
In d, after a portion having a small curvature connected to both sides is brought into close contact, it moves from the first molding surface 2 side to the second molding surface 21 side and adheres. As a result, the convex bending portions 30c and 30d of the molten resin sheet 30m that are located on the opening side of the concave portion 2a of the first molding surface 2
Is thin in the direction along the surface, and is stretched in the direction along the surface when it is brought into close contact with the second molding surface 21, so that the thickness tends to be somewhat thin, but this is not particularly problematic. However, the concave bent portion 30 formed on the side of the molten resin sheet 30m on the bottom side of the concave portion 2a
Since a and 30b have a surplus in the direction along the surface and are pressed and shrunk in the direction along the surface when they are brought into close contact with the second molding surface 21, the molten resin sheet 30m has this as shown in FIG. Wrinkles are formed on portions on the back side of the concave bent portions 30a and 30b, and unevenness occurs. For this reason, the components to be mounted near this rise from the back surface of the plate-shaped product 30 and the mounting accuracy and the mounting strength are reduced, or the surface of the plate-shaped product 30 is glossy or shrunk corresponding to the unevenness and the appearance is reduced. Problem arises. An object of the present invention is to solve such a problem.

[0010]

SUMMARY OF THE INVENTION A matched die forming method according to the present invention comprises a lower die having a first forming surface having a concave portion formed on an upper side, and a lower die which is provided so as to be able to approach and separate from the lower die. In a matched die molding method using an upper die having a second molding surface formed on a lower side where a gap between the first molding surface and the first molding surface is substantially constant, a molten resin sheet having a thickness smaller than the gap is first molded. The molten resin sheet is first brought into close contact with almost the entire first molding surface,
The two resin molds are positioned closest to each other, and then the molten resin sheet near the bottom of the recess is brought into close contact with the second molding surface, and then the molten resin sheet near the bottom of the recess is brought into close contact with the second molding surface. Things. The adhesion of the molten resin sheet to the second molding surface of the upper mold is performed by firstly adhering the molten resin sheet near the bottom of the concave portion to the second molding surface together with the concave bent portion formed on the side thereof. The other part is in close contact with the second molding surface. As described above, the concave bent portion is in close contact with the second molding surface before the side opposite to the bottom of the concave portion of the small curvature portion connected to both sides thereof is in close contact with the second molding surface. The concave bend is not compressed in the direction along the surface.

[0011] The invention of the preceding paragraph is characterized in that the lower die has a first passage having a plurality of narrow first communication holes opened in the first molding surface near the bottom of the recess, and a first passage other than near the bottom of the recess. An upper side having a plurality of narrow second communication holes opened in the molding surface and forming a second passage not communicating with the first passage, and having a large number of narrow upper suction holes opening in the second molding surface in the upper mold. A passage is formed, and close contact of the molten resin sheet to almost the entire surface of the first molding surface is performed by applying a negative pressure to the first passage and the second passage. It is preferable to apply the positive pressure to the first passage by applying a positive pressure to the first molten resin sheet, and to apply the negative pressure to the upper passage by applying the negative pressure to the upper passage.

The close contact of the molten resin sheet on the second molding surface other than near the bottom of the concave portion according to the invention of the preceding paragraph can be achieved by applying the negative pressure to the upper passage instead of or together with applying the negative pressure to the upper passage.
This may be performed by applying a positive pressure to the passage.

Further, the matched die forming apparatus according to the present invention includes a lower mold having a first molding surface having a concave portion formed on an upper side, and a lower mold provided so as to be capable of approaching and separating from the lower mold. In a matched die forming apparatus including an upper mold having a second molding surface formed on the lower side with a substantially constant gap therebetween, a plurality of molds formed in the lower mold and opening to the first molding surface near the bottom of the recess. A first passage having a narrow first communication hole, and a plurality of narrow second communication holes formed in the lower die and opening to a first molding surface other than near the bottom of the concave portion, and communicating with the first passage. A second passage that is not provided, and an upper passage having a large number of narrow upper suction holes formed in the upper die and opening to the second molding surface. By applying a negative pressure to the first passage and the second passage, the molten resin sheet is first brought into close contact with almost the entire surface of the first molding surface, and by applying a positive pressure to the first passage, the molten resin sheet is brought into contact with the bottom of the concave portion and slightly outside thereof. The molten resin sheet thus formed is adhered from the first molding surface to the second molding surface, and by applying a negative pressure to the upper passage, the other molten resin sheet is also adhered to the second molding surface from the first molding surface. The adhesion of the molten resin sheet other than the above to the second molding surface may be performed by applying a positive pressure to the second passage instead of or together with applying the negative pressure to the upper passage.

[0014]

1 and 2, an embodiment of a matched die forming method and a matched die forming apparatus used in the method according to the present invention will be described. The plate-shaped product 30 manufactured according to this embodiment is obtained by covering the outer surface of a rigid base material 31 with a thin flexible skin 32,
Its thickness is almost constant.

First, a description will be given of a matched die forming apparatus according to this embodiment. This matched die forming apparatus includes a lower die 10 attached to a lower fixed die support member (not shown) and an upper die 20 attached to an upper movable die support member (not shown). The upper mold 20 and the supply die 35 are substantially the same as those of the related art described with reference to FIGS. 3 to 6, and the lower mold 10 is different from the related art only in the passage formed therein. The supply die 35 for supplying the molten resin sheet 30m from the resin supply device is substantially the same as the conventional technique described with reference to FIGS.

On the first molding surface 11 on the upper side of the lower mold 10, a large concave portion 11a similar to the above-mentioned prior art is formed, and in the lower mold 10, an area substantially corresponding to the concave portion 11a in plan view. A first intermediate chamber 16A is formed in the other area, and a second intermediate chamber 16B is formed in the other area.
The first intermediate chamber 16A communicates with a large number of narrow first passages 15A opening on the first molding surface 11 serving as the bottom of the concave portion 11a and a first port 18A opening on the bottom surface of the lower mold 10. The intermediate chamber 16A, the first communication hole 17A, and the first port 18A form a first passage 15A. In the second intermediate chamber 16B, a large number of narrow second passages 15B opening to the first molding surface 11 other than the bottom of the concave portion 11a,
The second intermediate chamber 16B, the second communication hole 17B, and the second port 18B are communicated with each other.
B is a second passage 15B that is not communicated with the first passage 15A.
Is formed. Each of the ports 18A and 18B has a vacuum source comprising a vacuum pump, a vacuum tank and an on-off valve, respectively.
A compressed air source (both not shown) including a compression pump, a compression tank, and an on-off valve is connected.

A convex portion 21a corresponding to the concave portion 11a of the lower die 10 is formed on a second molding surface 21 serving as a lower surface of the upper die 20 provided so as to be able to approach and separate from the lower die 10 from above.
At the position where the two dies 10, 20 are closest (see FIGS. 1 and 2), the gap between the two molding surfaces 11, 21 is almost constant. The upper intermediate chamber 26 formed in the upper mold 20 has a number of upper suction holes 27 opened in the second molding surface 21.
And an upper port 28 that opens to the upper surface of the upper die 20. The upper intermediate chamber 26, the upper suction hole 27, and the upper port 28 form an upper passage 25. Upper port 28
Is connected to a vacuum source (not shown) including a vacuum pump, a vacuum tank, and an on-off valve. On the second molding surface 21 of the upper die 20, a grain pattern is formed to be transferred to a skin 32 which is a design surface of the plate-shaped product 30.

Next, a method of forming a matched die according to this embodiment will be described. Also in this embodiment, similarly to the above-described prior art, the molten resin sheet 30m including the base molten resin layer 31m and the skin molten resin layer 32m extruded from the supply die 35 has the base molten resin layer 31m side down. The lower die 10 is supplied so as to cover the entire first molding surface 11, and the entire surface is suction-contacted to the first molding surface 11 of the lower die 10. 15A
3 and FIG. 4 except that the process is performed by applying a negative pressure from a vacuum source to both the second passage 15B and the second passage 15B.

The molten resin sheet 30 m on the first molding surface 11
After the suction and close contact, the supply die 35 is completely retracted to the side from above the lower die 10 and then, as shown in FIG.
0 is lowered to the closest position. In this state as well, as in the above-described prior art, the protrusion 22 on the outer periphery of the upper mold 20 is fixed to the lower mold 1
0 abuts on the upper surface of the outer peripheral portion of the first molding surface 11, unnecessary portions on the outer periphery of the molten resin sheet 30 m are cut off, and the outer skin molten resin layer 32 m on the upper side of the molten resin sheet 30 m and the second molding surface 21 of the upper mold 20. There are some gaps between them. Upper passage 25
An upper port 28 of the upper passage 25 is communicated with the atmosphere.

Next, the positive pressure from the compressed air source is applied to the first passage 15A of the lower mold 10 via the first port 18A.
As a result, the molten resin sheet 30m first has a small curvature portion serving as the bottom of the concave portion 11a.
Immediately after being pressed and adhered to the first molding surface 1a, the concave bent portions 30a and 30b having large curvatures on both sides thereof are formed into the convex portions 2 of the second molding surface 21.
1a, and then close to the second molding surface 21 up to the outer portion having a smaller curvature, and the resulting gap between the molten resin sheet 30m and the first molding surface 11 becomes the second passage. When the pressure reaches a part of the second communication hole 17B of the hole 15B (see FIG. 1), the positive pressure in this gap leaks to the second passage 15B side and the positive pressure decreases, so the range of this gap further increases. Disappears.

Subsequently, a negative pressure from a vacuum source is applied to the upper passage 25 of the upper mold 20 via the upper port 28 to apply a negative pressure to the gap remaining between the molten resin sheet 30m and the second molding surface 21. At the same time, the application of the negative pressure to the second passage 15B is stopped and the second port 18B is communicated with the atmosphere, so that the molten resin sheet 30m has been in close contact with the first molding surface 11 side up to that point. The portion is also brought into close contact with the second molding surface 21 by suction. As a result, the molten resin sheet 30m is entirely sucked toward the upper mold 20 as shown in FIG. 2, and the skin molten resin layer 32m is brought into close contact with the second molding surface 21 so that the grain pattern of the second molding surface 21 is reduced. It is transferred to the surface of the skin melt resin layer 32m. Then, the temperature of the molten resin sheet 30m is lowered by natural cooling or forced cooling to be cured, and the base material 31 is cooled.
When the plate-like product 30 is formed, the application of the negative pressure to the upper passage 25 is stopped.
After communicating 8 with the atmosphere, the upper die 20 is raised to take out the plate-like product 30. Subsequently, the supply die 35 is moved onto the lower mold 10 again, and the molten resin sheet 3 is moved in the same manner as described above.
0 m is extruded to start forming the next plate-shaped product 30.

According to the above-described embodiment, first, the molten resin sheet 30m is pressed into close contact with the convex portion 21a of the second molding surface 21 at the bottom portion of the concave portion 11a with a small curvature, and then immediately on both sides thereof. Concave curvature portion 30a having a large curvature of
30b is pressed and adhered to the protrusion 21a of the second molding surface 21. In other words, the concave bent portions 30a and 30b are formed on the second molding surface 2 before the side opposite to the bottom of the concave portion 11a among the small curvature portions connected to both sides thereof is brought into close contact with the second molding surface 21.
1 so that the molten resin sheet 3
The 0 m concave bent portions 30a and 30b are not compressed in the direction along the surface. Therefore, no wrinkles are formed on the back side of the concave bent portions 30a and 30b of the plate-shaped product 30 to cause unevenness. And the surface of the plate-shaped product 30 that becomes the concave bent portions 30a and 30b is not glossy or shrunk, and the appearance is not deteriorated.

In the above-described embodiment, the first passage 15A and the second passage 15
B, an upper passage 25 is formed in the upper mold 20, and a negative pressure or a positive pressure is applied to each of these passages in a predetermined order so that the molten resin sheet 3 with respect to the first molding surface 11 and the second molding surface 21 is formed.
Since the above-described molding is performed by controlling the close contact of 0 m, control for such molding can be easily and reliably performed.

In the above-described embodiment, the portion of the molten resin sheet 30m that is not in close contact with the second molding surface 21 due to the positive pressure from the first passage 15A is applied by applying a negative pressure to the upper passage 25. However, the close contact may be performed by applying a positive pressure to the second passage 15B instead of applying a negative pressure to the upper passage 25, or simultaneously applying a negative pressure to the upper passage 25 to the second passage 15B. You may perform so that a positive pressure may be given.

In the above-described embodiment, the sheet-like molten resin 30m is a two-layered sheet composed of the base material molten resin layer 31m and the skin molten resin layer 32m. A foaming agent is kneaded between the two sheets. It is also possible to form a three-layer structure by adding an intermediate molten resin layer to be a foamed layer, or to form a sheet-shaped molten resin by only one molten resin layer.

[0026]

According to the matched die forming method of the present invention, the concave bent portion of the molten resin sheet formed near the bottom of the concave portion of the lower die is opposite to the bottom portion of the concave portion in the small curvature portion connected to both sides thereof. Since the side to be formed is brought into close contact with the second molding surface before being brought into close contact with the second molding surface, the concave bent portion of the molten resin sheet is not compressed in the direction along the surface. Therefore, no wrinkles are formed on the back side of the plate-shaped product serving as this part, and irregularities are not generated.Parts to be mounted in the vicinity thereof are precisely mounted on the back side of the plate-shaped product, so that mounting accuracy and mounting strength are improved, and The surface of the plate-shaped product serving as the concavely bent portion does not suffer from uneven gloss or shrinkage, and the appearance does not deteriorate.

In the above invention, a first passage and a second passage not communicating with the first passage are formed in the lower mold, and an upper passage is formed in the upper mold, and a negative pressure or a positive pressure is applied to each of these passages. According to the two inventions in which the adhesion of the molten resin sheet to the first molding surface and the second molding surface is controlled by giving in this order, such adhesion control can be performed easily and reliably.

Further, according to the matched die forming apparatus of the present invention, a negative pressure or a positive pressure is applied to the first passage, the second passage and the upper passage in a predetermined order, and the melt is supplied to the first molding surface of the lower die. Adhesion of the resin sheet to the first molding surface and the second molding surface can be controlled. Therefore, the plate-shaped product formed by the present invention improves the mounting accuracy and the mounting strength of the parts to be mounted in the vicinity of the concave bent portion so that no irregularities are formed on the back side, as in the above-mentioned inventions. Let
In addition, it is possible to prevent the appearance of the plate-shaped product serving as the concave bent portion from being deteriorated due to uneven gloss or shrinkage, and it is possible to easily and reliably control the above-mentioned close contact.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a state in which a molten resin sheet near the bottom of a concave portion of an upper mold is brought into close contact with a second molding surface of an upper mold according to an embodiment of the matched die molding method and the matched die molding apparatus according to the present invention. is there.

FIG. 2 is a cross-sectional view of the embodiment shown in FIG. 1, showing a state in which a molten resin sheet other than near the bottom of a recess is also in close contact with a second molding surface.

FIG. 3 is a cross-sectional view showing a state in which a molten resin sheet is supplied onto a lower mold of an example of a matched die forming method and a matched die forming apparatus according to a conventional technique.

4 is a cross-sectional view showing a state in which a molten resin sheet supplied onto a lower mold is attracted to and adhered to a first molding surface according to the related art shown in FIG.

FIG. 5 is a perspective view of the lower mold 1 shown in FIG.
FIG. 4 is a cross-sectional view showing a state in which it is closest to zero.

FIG. 6 shows a state in which the molten resin sheet is placed on the second die of the upper mold in FIG.
FIG. 3 is a cross-sectional view showing a state in which it is in close contact with a molding surface.

[Explanation of symbols]

10 lower mold, 11 first molding surface, 11a recess, 15A
... 1st passage, 15B ... 2nd passage, 17A ... 1st communication hole,
17B: second communication hole, 20: upper die, 21: second molding surface,
25 ... upper passage, 27 ... upper suction hole, 30 m ... molten resin sheet.

Claims (4)

[Claims] 1. A lower mold having a first molding surface having a concave portion formed on an upper side thereof, and a gap between the lower mold and the first molding surface at a closest position. In a matched die molding method using an upper mold having a constant second molding surface formed on a lower side, a molten resin sheet having a thickness smaller than the gap is supplied so as to cover the first molding surface. First, the resin sheet is brought into close contact with almost the entire surface of the first molding surface, and the molten resin sheet, which is near the bottom of the concave portion, is brought into close contact with the second molding surface after the two molds are positioned closest to each other. Characterized in that the molten resin sheet other than near the bottom is closely adhered to the second molding surface. 2. The lower die has a first passage having a plurality of narrow first communication holes opened in the first molding surface near the bottom of the recess, and a first passage other than near the bottom of the recess. A second passage is formed which has a plurality of thin second communication holes opened on the first molding surface and is not communicated with the first passage, and a number of narrow upper openings opened on the second molding surface in the upper mold. An upper passage having a suction hole is formed, and the close contact of the molten resin sheet to almost the entire surface of the first molding surface is performed by applying a negative pressure to the first passage and the second passage. The close contact of the molten resin sheet near the bottom of the concave portion is performed by applying a positive pressure to the first passage, and the close contact of the molten resin sheet other than near the bottom of the concave portion with the second molding surface is the upper side. Performed by applying negative pressure to the passage The method for forming a matched die according to claim 1, wherein: 3. The close contact of the molten resin sheet on the second molding surface other than near the bottom of the concave portion may apply a positive pressure to the second passage instead of or together with applying a negative pressure to the upper passage. The method according to claim 2, wherein the method is performed by giving. 4. A lower mold in which a first molding surface having a concave portion is formed on an upper side, and is provided so as to be able to approach and separate from the lower mold. In a matched die forming apparatus including an upper mold having a constant second molding surface formed on a lower side, a plurality of narrow first molding surfaces formed in the lower mold and opening to the first molding surface near a bottom of the concave portion. A first passage having one communication hole, and a plurality of narrow second communication holes formed in the lower die and opening to the first molding surface other than near the bottom of the concave portion; A matched die forming apparatus, comprising: a second passage that is not communicated; and an upper passage having a large number of narrow upper suction holes formed in the upper die and opening to the second molding surface.